We quit feeding ours regular dog food about 4 years ago. We were spending easily $150/month on food that left MASSIVE piles in the back yard!
We switched to feeding them raw chicken necks and chicken backs that we buy in bulk from a butcher down the road. They have become much healthier, only costs us about $72/month to feed them, and the best part is I haven't had to pick up their crap since we switched! there is hardly any to begin with since they digest I would guess better than 80% of their food, and it ends up turning to dust and blowing away within a few days! (sorry for anyone that was eating while reading this post
We usually go through about 120 Lbs. of food a month now.